Correctly account for unrealised gains across multiple years

README.md

@@ -56,6 +56,8 @@ Ledger-pyreport by default observes the convention that positive amounts in Ledg
 
 A commodity which has *any* price data in Ledger (including those specified through `@` or `@@`, or explicitly through `P`) will be regarded as a commodity measured at fair market value, and automatically revalued accordingly. A commodity which has *no* price data in Ledger (i.e. lot prices through `{…}` or `{{…}}` only) will be regarded as a commodity measured at historical cost, and will not be subsequently revalued.
 
+In accordance with accrual accounting, unrealised gains are charged to the Unrealized Gains income/expense account shown in *config.yml* in the period in which they occur. Subsequent realisations of those gains should be charged against the Unrealized Gains account within the Ledger journal. Alternatively, if charged to a different account (e.g. a realised Capital Gains income account), note that the Unrealized Gains account will contain a *contra* balance corresponding to previous years gains which are now realised.
+
 ## Comparative statements
 
 ledger-pyreport can be used to produce comparative statements, for example ‘compare *n* years’ or ‘compare *n* months’.

ledger_pyreport/accounting.py

@@ -47,19 +47,22 @@ def trial_balance(ledger, date, pstart, commodity, label=None):
 	
 	for account in set(list(r_date.keys()) + list(r_pstart.keys())):
 		if account in r_pstart:
-			# Charge previous unrealized gains to Accumulated OCI
+			tb_date.balances[account.name] = tb_date.get_balance(account) + r_pstart[account].postings[0].amount
-			#r_pstart[account].postings[1].account = ledger.get_account(config['accumulated_oci'])
+			if r_pstart[account].postings[1].account.is_income or r_pstart[account].postings[1].account.is_expense:
-			accumulated = r_pstart[account].postings[0].amount
+				tb_date.balances[config['retained_earnings']] = tb_date.get_balance(ledger.get_account(config['retained_earnings'])) - r_pstart[account].postings[0].amount
+			elif r_pstart[account].postings[1].account.is_oci:
+				tb_date.balances[config['accumulated_oci']] = tb_date.get_balance(ledger.get_account(config['accumulated_oci'])) - r_pstart[account].postings[0].amount
+			else:
+				tb_date.balances[config['unrealized_gains']] = tb_date.get_balance(ledger.get_account(config['accumulated_oci'])) - r_pstart[account].postings[0].amount
 			
-			tb_date.balances[account.name] = tb_date.get_balance(account) + accumulated
+			# Reversing entry
-			tb_date.balances[config['accumulated_oci']] = tb_date.get_balance(ledger.get_account(config['accumulated_oci'])) - accumulated
+			trn_reversal = r_pstart[account].reverse(None, pstart, '<Reversal of Unrealized Gains>')
+			ledger.transactions.insert(0, trn_reversal)
+			
+			tb_date.balances[account.name] = tb_date.get_balance(account) + trn_reversal.postings[0].amount
+			tb_date.balances[config['unrealized_gains']] = tb_date.get_balance(ledger.get_account(config['unrealized_gains'])) - trn_reversal.postings[0].amount
 		
 		if account in r_date:
-			if account in r_pstart:
-				# Adjust for this year's unrealized gains only
-				r_date[account].postings[0].amount -= accumulated
-				r_date[account].postings[1].amount += accumulated
-			
 			tb_date.balances[account.name] = tb_date.get_balance(account) + r_date[account].postings[0].amount
 			tb_date.balances[config['unrealized_gains']] = tb_date.get_balance(ledger.get_account(config['unrealized_gains'])) - r_date[account].postings[0].amount
 	

ledger_pyreport/model.py

@@ -84,6 +84,11 @@ class Transaction:
 			result.append('    {}  {}'.format(posting.account.name, posting.amount.tostr(False)))
 		return '\n'.join(result)
 	
+	def reverse(self, id, date, description, code=None, uuid=None):
+		result = Transaction(self.ledger, id, date, description, code, uuid)
+		result.postings = [Posting(p.transaction, p.account, -p.amount, p.comment, p.state) for p in self.postings]
+		return result
+	
 	@property
 	def has_comment_detail(self):
 		return any(p.comment for p in self.postings)