Transaction price allocated to remaining performance obligations

  
As of December 31, 2021, we had $7.8 billion of transaction price allocated to remaining performance obligations related to executed contracts with an original duration of one year or more, which are primarily included in the Americas segment. Some contracts in the United States included in this amount contain index-dependent price increases, which are not known at this time. We expect to recognize approximately 35% of this amount as revenue in 2022, 30% in 2023, 15% in each of 2024 and 2025, and 5% in 2026.Significant JudgmentsRevenues from product sales are recorded at the net sales price (transaction price), which includes estimates of variable consideration primarily related to rebates and wholesaler chargebacks. These reserves are based on estimates of the amounts earned or to be claimed on the related sales and are included in accrued expenses and other current liabilities and accounts receivable, net on the consolidated balance sheets. Management's estimates take into consideration historical experience, current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. Overall, these reserves reflect our best estimates of the amount of consideration to which we are entitled based on the terms of the contract using the expected value method. The amount of variable consideration included in the net sales price is limited to the amount that is probable not to result in a significant reversal in the amount of the cumulative revenue recognized in a future period. Revenue recognized in the years ended December 31, 2021, 2020 and 2019 related to performance obligations satisfied in prior periods was not material. Additionally, our contracts with customers often include promises to transfer multiple products and services to a customer. Determining whether products and services are considered distinct performance obligations that should be accounted for separately and determining the allocation of the transaction price may require significant judgment.Practical Expedients We apply a practical expedient to expense as incurred costs to obtain a contract with a customer when the amortization period would have been one year or less. We do not disclose the value of the transaction price that is allocated to unsatisfied performance obligations for contracts with an original expected length of less than one year. We have elected to use the practical expedient to not adjust the promised amount of consideration for the effects of a significant financing component if it is expected, at contract inception, that the period between when we transfer a promised good or service to a customer and when the customer pays for that good or service will be one year or less. Additionally, all taxes assessed by a governmental authority that are both imposed on and concurrent with a specific revenue-producing transaction and collected from a customer are excluded from revenue.Accounts Receivable and Allowance for Doubtful AccountsIn the normal course of business, we provide credit to our customers, perform credit evaluations of these customers and maintain reserves for potential credit losses. In determining the amount of the allowance for doubtful accounts, we consider, among other items, historical credit losses, the past-due status of receivables, payment histories, other customer-specific information, current economic conditions and reasonable and supportable future forecasts. Receivables are written off when we determine they are uncollectible. The following table summarizes the allowance for doubtful accounts.

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| --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  |  |  |  |  |  |  |  |  |
| years ended December 31(in millions) | 2021 | 2020 |
| Balance at beginning of period | $ | 125  |  | $ | 112  |  |
| Acquisition | 13  |  | —  |  |
| Adoption of new accounting standard | —  |  | 4  |  |
| Charged to costs and expenses | (2) |  | 11  |  |
| Write-offs | (5) |  | (4) |  |
| Currency translation adjustments | (9) |  | 2  |  |
|  |  |  |
| Balance at end of period | $ | 122  |  | $ | 125  |  |

  
Shipping and Handling CostsShipping costs, which are costs incurred to physically move product from our premises to the customer’s premises, are classified as selling, general and administrative (SG&A) expenses. Handling costs, which are costs incurred to 54
