diff --git a/conservancy_beancount/reconcile/statement_reconciler.py b/conservancy_beancount/reconcile/statement_reconciler.py
index 6343ed5..df665ed 100644
--- a/conservancy_beancount/reconcile/statement_reconciler.py
+++ b/conservancy_beancount/reconcile/statement_reconciler.py
@@ -58,7 +58,7 @@ from typing import Callable, Dict, List, Tuple, TextIO
 
 from beancount import loader
 from beancount.query.query import run_query
-from colorama import Fore, Style
+from colorama import Fore, Style  # type: ignore
 
 if not sys.warnoptions:
     import warnings
@@ -96,7 +96,7 @@ JUNK_WORDS = [
 JUNK_WORDS_RES = [re.compile(word, re.IGNORECASE) for word in JUNK_WORDS]
 ZERO_RE = re.compile('^0+')
 
-def remove_duplicate_words(text):
+def remove_duplicate_words(text: str) -> str:
     unique_words = []
     known_words = set()
     for word in text.split():
@@ -123,18 +123,19 @@ def remove_payee_junk(payee: str) -> str:
     payee.strip()
     return payee
 
-# NOTE: Statement doesn't seem to give us a running balance or a final total.
 
 def read_transactions_from_csv(f: TextIO, standardize_statement_record: Callable) -> list:
     reader = csv.DictReader(f)
-    return sort_records([standardize_statement_record(row, reader.line_num) for row in reader])
+    # The reader.line_num is the source line number, not the spreadsheet row
+    # number due to multi-line records.
+    return sort_records([standardize_statement_record(row, i) for i, row in enumerate(reader, 2)])
 
-# Does the account you entered match the CSV?
-# Is the CSV in the format we expect? (ie. did they download through the right interface?)
-# Logical CSV line numbers
-# CSV reconciliation report
+
+# NOTE: Statement doesn't seem to give us a running balance or a final total.
+# CSV reconciliation report.
 # Merge helper script.
 
+
 def standardize_amex_record(row: Dict, line: int) -> Dict:
     """Turn an AMEX CSV row into a standard dict format representing a transaction."""
     return {
@@ -148,6 +149,20 @@ def standardize_amex_record(row: Dict, line: int) -> Dict:
     }
 
 
+def validate_amex_csv(sample: str, account: str) -> None:
+    required_cols = {'Date', 'Amount', 'Description', 'Card Member'}
+    reader = csv.DictReader(io.StringIO(sample))
+    if reader.fieldnames and not required_cols.issubset(reader.fieldnames):
+        sys.exit(f"This CSV doesn't seem to have the columns we're expecting, including: {', '.join(required_cols)}")
+
+
+def validate_fr_csv(sample: str, account: str) -> None:
+    required_cols = {'Date', 'Amount', 'Detail', 'Serial Num'}
+    reader = csv.DictReader(io.StringIO(sample))
+    if reader.fieldnames and not required_cols.issubset(reader.fieldnames):
+        sys.exit(f"This CSV doesn't seem to have the columns we're expecting, including: {', '.join(required_cols)}")
+
+
 def standardize_fr_record(row: Dict, line: int) -> Dict:
     return {
         'date': datetime.datetime.strptime(row['Date'], '%m/%d/%Y').date(),
@@ -181,7 +196,7 @@ def format_record(record: dict) -> str:
     return output
 
 
-def format_multirecord(r1s, r2s, note):
+def format_multirecord(r1s: list[dict], r2s: list[dict], note: str) -> list[list]:
     total = sum(x['amount'] for x in r2s)
     assert len(r1s) == 1
     assert len(r2s) > 1
@@ -191,26 +206,29 @@ def format_multirecord(r1s, r2s, note):
         match_output.append([r1s[0]['date'], f'{r1s[0]["date"].isoformat()}:             ↳                                    →  {format_record(r2)}  ✓ Matched{note}'])
     return match_output
 
+
 def sort_records(records: List) -> List:
     return sorted(records, key=lambda x: (x['date'], x['amount']))
 
 
-def first_word_exact_match(a, b):
+def first_word_exact_match(a: str, b: str) -> float:
     if len(a) == 0 or len(b) == 0:
-        return 0
+        return 0.0
     first_a = a.split()[0].strip()
     first_b = b.split()[0].strip()
     if first_a.casefold() == first_b.casefold():
         return min(1.0, 0.2 * len(first_a))
     else:
-        return 0;
+        return 0.0;
 
-def payee_match(a, b):
-    fuzzy_match = fuzz.token_set_ratio(a, b) / 100.00
+
+def payee_match(a: str, b: str) -> float:
+    fuzzy_match = float(fuzz.token_set_ratio(a, b) / 100.00)
     first_word_match = first_word_exact_match(a, b)
     return max(fuzzy_match, first_word_match)
 
-def records_match(r1: Dict, r2: Dict) -> Tuple[bool, str]:
+
+def records_match(r1: Dict, r2: Dict) -> Tuple[float, List[str]]:
     """Do these records represent the same transaction?"""
 
     date_score = date_proximity(r1['date'], r2['date'])
@@ -254,7 +272,7 @@ def records_match(r1: Dict, r2: Dict) -> Tuple[bool, str]:
     return overall_score, overall_message
 
 
-def match_statement_and_books(statement_trans: list, books_trans: list):
+def match_statement_and_books(statement_trans: List[Dict], books_trans: List[Dict]) -> Tuple[List[Tuple[List, List, List]], List[Dict], List[Dict]]:
     """
     Runs through all the statement transactions to find a matching transaction
     in the books. If found, the books transaction is marked off so that it can
@@ -266,9 +284,9 @@ def match_statement_and_books(statement_trans: list, books_trans: list):
     remaining_statement_trans = []
 
     for r1 in statement_trans:
-        best_match_score = 0
+        best_match_score = 0.0
         best_match_index = None
-        best_match_note = ''
+        best_match_note = []
         matches_found = 0
         for i, r2 in enumerate(books_trans):
             score, note = records_match(r1, r2)
@@ -280,7 +298,8 @@ def match_statement_and_books(statement_trans: list, books_trans: list):
         if best_match_score > 0.5 and matches_found == 1 and 'check-id mismatch' not in best_match_note or best_match_score > 0.8:
             matches.append(([r1], [books_trans[best_match_index]], best_match_note))
             # Don't try to make a second match against this books entry.
-            del books_trans[best_match_index]
+            if best_match_index is not None:
+                del books_trans[best_match_index]
         else:
             remaining_statement_trans.append(r1)
     for r2 in books_trans:
@@ -288,7 +307,9 @@ def match_statement_and_books(statement_trans: list, books_trans: list):
     return matches, remaining_statement_trans, remaining_books_trans
 
 
-def format_matches(matches, csv_statement: str, show_reconciled_matches):
+# TODO: Return list of tuples (instead of list of lists).
+
+def format_matches(matches: List, csv_statement: str, show_reconciled_matches: bool) -> List[List]:
     match_output = []
     for r1s, r2s, note in matches:
         note = ', '.join(note)
@@ -306,14 +327,15 @@ def format_matches(matches, csv_statement: str, show_reconciled_matches):
     return match_output
 
 
-def date_proximity(d1, d2):
-    diff = abs((d1 - d2).days)
+def date_proximity(d1: datetime.date, d2: datetime.date) -> float:
+    diff = abs(int((d1 - d2).days))
     if diff > 60:
-        return 0
+        return 0.0
     else:
         return 1.0 - (diff / 60.0)
 
-def metadata_for_match(match, statement_filename, csv_filename):
+
+def metadata_for_match(match: Tuple[List, List, List], statement_filename: str, csv_filename: str) -> List[Tuple[str, int, str]]:
     # Can we really ever have multiple statement entries? Probably not.
     statement_filename = get_repo_relative_path(statement_filename)
     csv_filename = get_repo_relative_path(csv_filename)
@@ -361,15 +383,18 @@ def write_metadata_to_books(metadata_to_apply: List[Tuple[str, int, str]]) -> No
             f.writelines(contents)
             print(f'Wrote {filename}.')
 
-def get_repo_relative_path(path):
+
+def get_repo_relative_path(path: str) -> str:
     return os.path.relpath(path, start=os.getenv('CONSERVANCY_REPOSITORY'))
 
-def parse_path(path):
+
+def parse_path(path: str) -> str:
     if not os.path.exists(path):
         raise argparse.ArgumentTypeError(f'File {path} does not exist.')
     return path
 
-def parse_repo_relative_path(path):
+
+def parse_repo_relative_path(path: str) -> str:
     if not os.path.exists(path):
         raise argparse.ArgumentTypeError(f'File {path} does not exist.')
     repo = os.getenv('CONSERVANCY_REPOSITORY')
@@ -379,7 +404,8 @@ def parse_repo_relative_path(path):
         raise argparse.ArgumentTypeError(f'File {path} does not share a common prefix with $CONSERVANCY_REPOSITORY {repo}.')
     return path
 
-def parse_args(argv):
+
+def parse_args(argv: List[str]) -> argparse.Namespace:
     parser = argparse.ArgumentParser(description='Reconciliation helper')
     parser.add_argument('--beancount-file', required=True, type=parse_path)
     parser.add_argument('--csv-statement', required=True, type=parse_repo_relative_path)
@@ -392,7 +418,8 @@ def parse_args(argv):
     parser.add_argument('--non-interactive', action='store_true', help="Don't prompt to write to the books")
     return parser.parse_args(args=argv[1:])
 
-def totals(matches):
+
+def totals(matches: List[Tuple[List, List, List]]) -> Tuple[decimal.Decimal, decimal.Decimal, decimal.Decimal]:
     total_matched = decimal.Decimal(0)
     total_missing_from_books = decimal.Decimal(0)
     total_missing_from_statement = decimal.Decimal(0)
@@ -406,16 +433,16 @@ def totals(matches):
     return total_matched, total_missing_from_books, total_missing_from_statement
 
 
-def subset_match(statement_trans, books_trans):
+def subset_match(statement_trans: List[dict], books_trans: List[dict]) ->  Tuple[List[Tuple[List, List, List]], List[Dict], List[Dict]]:
     matches = []
     remaining_books_trans = []
     remaining_statement_trans = []
 
     groups = itertools.groupby(books_trans, key=lambda x: (x['date'], x['payee']))
     for k, group in groups:
-        best_match_score = 0
+        best_match_score = 0.0
         best_match_index = None
-        best_match_note = ''
+        best_match_note = []
         matches_found = 0
 
         group_items = list(group)
@@ -430,11 +457,11 @@ def subset_match(statement_trans, books_trans):
                 best_match_index = i
                 best_match_note = note
         if best_match_score > 0.5 and matches_found == 1 and 'check-id mismatch' not in best_match_note or best_match_score > 0.8:
-            if best_match_score <= 0.8:
-                best_match_note.append('only one decent match')
             matches.append(([statement_trans[best_match_index]], group_items, best_match_note))
-            del statement_trans[best_match_index]
+            if best_match_index is not None:
+                del statement_trans[best_match_index]
             for item in group_items:
+                # TODO: Why?
                 books_trans.remove(item)
         else:
             remaining_books_trans.append(r2)
@@ -442,26 +469,33 @@ def subset_match(statement_trans, books_trans):
          remaining_statement_trans.append(r1)
     return matches, remaining_statement_trans, remaining_books_trans
 
-def process_unmatched(statement_trans, books_trans):
-    matches = []
+
+def process_unmatched(statement_trans: List[dict], books_trans: List[dict]) -> List[Tuple[List, List, List]]:
+    matches: List[Tuple[List, List, List]] = []
     for r1 in statement_trans:
         matches.append(([r1], [], ['no match']))
     for r2 in books_trans:
         matches.append(([], [r2], ['no match']))
     return matches
 
-def main(args):
+
+def main(args: argparse.Namespace) -> None:
     # TODO: Should put in a sanity check to make sure the statement you're feeding
     # in matches the account you've provided.
 
     # TODO: Can we open the files first, then pass the streams on to the rest of the program?
 
     if 'AMEX' in args.account:
+        validate_csv = validate_amex_csv
         standardize_statement_record = standardize_amex_record
     else:
+        validate_csv = validate_fr_csv
         standardize_statement_record = standardize_fr_record
 
     with open(args.csv_statement) as f:
+        sample = f.read(200)
+        validate_csv(sample, args.account)
+        f.seek(0)
         statement_trans = read_transactions_from_csv(f, standardize_statement_record)
 
     begin_date = statement_trans[0]['date']
diff --git a/tests/test_reconcile.py b/tests/test_reconcile.py
index fc00ef5..b7085a3 100644
--- a/tests/test_reconcile.py
+++ b/tests/test_reconcile.py
@@ -218,7 +218,7 @@ def test_payee_mismatch_ok_when_only_one_that_amount_and_date():
     statement = [S3]
     books = [B3_payee_mismatch_1]
     assert match_statement_and_books(statement, books) == (
-        [([S3], [B3_payee_mismatch_1], ['payee mismatch', 'only one decent match'])],
+        [([S3], [B3_payee_mismatch_1], ['payee mismatch'])],
         [],
         [],
     )
@@ -255,8 +255,8 @@ def test_payee_matches_when_first_word_matches():
 def test_metadata_for_match(monkeypatch):
     monkeypatch.setenv('CONSERVANCY_REPOSITORY', '.')
     assert metadata_for_match(([S1], [B1], []), 'statement.pdf', 'statement.csv') == [
-        ('2022/imports.beancount', 777, '    bank-statement: statement.pdf'),
-        ('2022/imports.beancount', 777, '    bank-statement-csv: statement.csv:222'),
+        ('2022/imports.beancount', 777, '    bank-statement: "statement.pdf"'),
+        ('2022/imports.beancount', 777, '    bank-statement-csv: "statement.csv:222"'),
     ]
 
 def test_no_metadata_if_no_matches():