After marriage, most couples begin accumulating joint accounts. You'll likely want a joint bank account so that you can both access your money. Most couples who buy a home do so with a joint mortgage to ensure that both parties have a legal claim to the property in the event of a divorce (just for reference, you can put your name on a home's title without your name being on the actual mortgage loan) You're also likely to acquire joint credit cards.
Unless you keep the accounts you held as a single person open, those accounts will gradually "time out" and fall off of your credit report. The credit entries that remain will be the joint accounts that you share with your spouse. The credit bureaus report joint debts to both your credit report and your spouse's. So, although you and your husband or wife's credit report won't merge in the true sense, you can expect your credit records to look extremely similar after several years of building a financial life together.
The gradual merging of credit information rather than the credit reports themselves can either help or hinder your scores. If you happen to marry someone with an abysmal sense of financial responsibility, you'd best be ready to take on the bulk of bill-paying yourself. A single missed payment can wreck serious havoc on you and your spouse's credit scores.
Do I Owe My Husband's/Wife's Debts Aftter Marriage?
Community Property States and Defaulted Spousal Debt